Fix S3 assume-role options (#37)

.version

@@ -1 +1 @@
-0.8.3
+0.8.4

Gemfile.lock

@@ -1,34 +1,34 @@
 PATH
   remote: core
   specs:
-    bfs (0.8.3)
+    bfs (0.8.4)
 
 PATH
   remote: ftp
   specs:
-    bfs-ftp (0.8.3)
-      bfs (= 0.8.3)
+    bfs-ftp (0.8.4)
+      bfs (= 0.8.4)
       net-ftp-list
 
 PATH
   remote: gs
   specs:
-    bfs-gs (0.8.3)
-      bfs (= 0.8.3)
+    bfs-gs (0.8.4)
+      bfs (= 0.8.4)
       google-cloud-storage (~> 1.18)
 
 PATH
   remote: s3
   specs:
-    bfs-s3 (0.8.3)
+    bfs-s3 (0.8.4)
       aws-sdk-s3 (~> 1.38)
-      bfs (= 0.8.3)
+      bfs (= 0.8.4)
 
 PATH
   remote: scp
   specs:
-    bfs-scp (0.8.3)
-      bfs (= 0.8.3)
+    bfs-scp (0.8.4)
+      bfs (= 0.8.4)
       net-scp
 
 GEM

s3/lib/bfs/bucket/s3.rb

@@ -141,15 +141,20 @@ def init_client(**opts)
         config[:credentials] = opts[:credentials] if opts[:credentials]
         config[:credentials] ||= Aws::Credentials.new(opts[:access_key_id].to_s, opts[:secret_access_key].to_s) if opts[:access_key_id]
         config[:credentials] ||= Aws::SharedCredentials.new(profile_name: opts[:profile_name]) if opts[:profile_name]
-        config[:credentials] = Aws::AssumeRoleCredentials.new(
-          client: config[:credentials] ? Aws::STS::Client.new(credentials: config[:credentials]) : nil,
-          role_arn: opts[:assume_role],
-          role_session_name: SecureRandom.urlsafe_base64(12),
-        ) if opts[:assume_role]
+        config[:credentials] = assume_role_credentials(opts[:assume_role], config[:credentials]) if opts[:assume_role]
 
         Aws::S3::Client.new(config)
       end
 
+      def assume_role_credentials(role_arn, credentials = nil)
+        opts = {
+          role_arn: role_arn,
+          role_session_name: SecureRandom.urlsafe_base64(12),
+        }
+        opts[:client] = Aws::STS::Client.new(credentials: credentials) if credentials
+        Aws::AssumeRoleCredentials.new(**opts)
+      end
+
       def walk(pattern, **opts)
         prefix = pattern[%r{^[^*?\{\}\[\]]+/}]
         prefix = File.join(*[@prefix, prefix].compact) if @prefix